Referring to FIG. 1, which is a schematic communication diagram for a conventional mansion doorbell machine 1. A visitor 2 pushes the doorbell of the mansion doorbell machine 1, the mansion doorbell machine 1 therefore notifies related householder 3, and let the related householder 3 conduct audio and video communication with the visitor 2. If the related householder 3 thinks there is no problem with the visitor 2, then the related householder 3 pushes a key on an intercom to open the mansion door and let the visitor go in.
If the related householder 3 is at outside of the mansion, then this conventional entrance management is unable to let the visitor 2 go in. But sometimes the visitor 2 is an official with the duty to investigate a criminal case or a fire accident, or the visitor 2 is a householder at outside of the mansion who forgets to bring keys. These conditions are the motives of the present invention.